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It's more than just silt and sand down there. Deposits taken from deep under the seafloor reveal the intimate connection between the ocean and Earth's atmosphere, according to a new [...]

A 13th-14th-century map held in the Bodleian Library (the Gough Map and the oldest map of Great Britain) shows two 'lost' islands in Cardigan Bay offshore west Wales, United Kingdom. This study investigates historical sources, alongside geological and bathymetric evidence, and proposes a model of post-glacial coastal evolution that provides an explanation for the 'lost' islands and a hypothetical framework for future research: (1) during the Pleistocene, Irish Sea ice occupied the area from the north and west, and Welsh ice from the east, (2) a landscape of unconsolidated Pleistocene deposits developed seaward of a relict pre-Quaternary cliffline with a land surface up to ca. 30 m above present sea-level, (3) erosion proceeded along the lines of a template provided by a retreating shoreline affected by Holocene sea-level rise, shore-normal rivers, and surface run-off from the relict cliffline and interfluves, (4) dissection established islands occupying cores of the depositional landscape, and (5) continued down-wearing, marginal erosion and marine inundation(s) removed the two remaining islands by the 16th century. Literary evidence and folklore traditions provide support in that Cardigan Bay is associated with the 'lost' lowland of Cantre'r Gwaelod. The model offers potential for further understanding post-glacial evolution of similar lowlands along northwest European coastlines. Une carte des 13e et 14e siecles que detient la bibliotheque de Bodley (carte de Gough, carte la plus ancienne de Grande-Bretagne) montre deux iles << disparues >> dans la baie Cardigan au large a l'ouest du Pays de Galles, au Royaume-Uni. Cette etude examine des sources historiques, ainsi que des preuves geologiques et bathymetriques, et elle propose un modele devolution cotiere postglaciaire fournissant une explication de la disparition des iles et un cadre hypothetique aux fins de recherche future : (1) durant le Pleistocene, les glaces de la mer d'Irlande occupaient la region a partir du nord et de l'ouest, et les glaces galloises setendaient a partir de lest; (2) un paysage de depots non consolides du Pleistocene s'est forme cote mer le long de falaises prequaternaires reliques, laissant emerger une surface terrestre atteignant jusqua environ 30 metres au-dessus du niveau actuei de la mer; (3) une erosion a suivi le long des lignes d'un modele cree par un rivage en recul affecte par la hausse du niveau de la mer de l'Holocene, les rivieres cotieres normales et lecoulement direct de surface des interfluves et de la ligne des falaises reliques; (4) une dissection a cree des iles occupant les coeurs du paysage de depot; (5) l'aplatissement continu, lerosion marginale et les inondations marines ont fait en sorte que les deux iles qui restaient avaient disparu au 16e siecle. Des preuves litteraires et des traditions folkloriques appuient l'association de la baie Cardigan avec les basses terres << disparues >> de Cantre'r Gwaelod. Le modele pourrait permettre une comprehension plus poussee de revolution postglaciaire des basses terres similaires le long des littoraux du nord-ouest de l'Europe., INTRODUCTION Cardigan Bay (Bae Ceredigion in Welsh) is a large embayment in the St. George's Channel situated on the west coast of mid-Wales, United Kingdom (UK), bounded to the north [...]

Author(s): Hai Cheng [sup.1] [sup.2] , R. Lawrence Edwards [sup.2] , Ashish Sinha [sup.3] , Christoph Spötl [sup.4] , Liang Yi [sup.5] , Shitao Chen [sup.6] , Megan Kelly [sup.2] [...], Oxygen isotope records from Chinese caves characterize changes in both the Asian monsoon and global climate. Here, using our new speleothem data, we extend the Chinese record to cover the full uranium/thorium dating range, that is, the past 640,000 years. The record&apos;s length and temporal precision allow us to test the idea that insolation changes caused by the Earth&apos;s precession drove the terminations of each of the last seven ice ages as well as the millennia-long intervals of reduced monsoon rainfall associated with each of the terminations. On the basis of our record&apos;s timing, the terminations are separated by four or five precession cycles, supporting the idea that the &apos;100,000-year&apos; ice age cycle is an average of discrete numbers of precession cycles. Furthermore, the suborbital component of monsoon rainfall variability exhibits power in both the precession and obliquity bands, and is nearly in anti-phase with summer boreal insolation. These observations indicate that insolation, in part, sets the pace of the occurrence of millennial-scale events, including those associated with terminations and &apos;unfinished terminations&apos;. Records of the Asian monsoon have been extended to 640,000 years ago, and confirm both that the 100,000-year ice age cycle results from integral numbers of precessional cycles and that insolation influences the pacing of major millennial-scale climate events. A 640,000-year record of the Asian monsoon Prior records of the Asian monsoon have revealed cyclic variations over hundreds of thousands of years, probably driven by variations in insolation caused by the precession of Earth&apos;s orbit. Hai Cheng and colleagues now provide a speleothem record from Chinese cave samples that extends earlier records to 640,000 years ago, close to the maximum age possible with uranium/thorium dating. This spectacular record confirms that the characteristic &apos;100,000-year&apos; ice age cycle corresponds to an integral number (four or five) of precession cycles, and that insolation influences millennial-scale variations in monsoon strength.

The major nutrients for phytoplankton growth (nitrogen, phosphorus and silicon) are supplied to the surface waters of the equatorial Pacific by wind-driven upwelling along the Equator. Their consumption by phytoplankton [...], The equatorial Pacific Ocean is one of the major high-nutrient, low-chlorophyll regions in the global ocean. In such regions, the consumption of the available macro-nutrients such as nitrate and phosphate is thought to be limited in part by the low abundance of the critical micro-nutrient iron (1). Greater atmospheric dust deposition (2) could have fertilized the equatorial Pacific with iron during the last ice age--the Last Glacial Period (LGP)--but the effect of increased ice-age dust fluxes on primary productivity in the equatorial Pacific remains uncertain (3-6). Here we present meridional transects of dust (derived from the [sup.232]Th proxy), phytoplankton productivity (using opal, [sup.231]Pa/[sup.230]Th and excess Ba), and the degree of nitrate consumption (using foraminifera-bound δ[sup.15]N) from six cores in the central equatorial Pacific for the Holocene (0-10,000 years ago) and the LGP (17,000-27,000 years ago). We find that, although dust deposition in the central equatorial Pacific was two to three times greater in the LGP than in the Holocene, productivity was the same or lower, and the degree of nitrate consumption was the same. These biogeochemical findings suggest that the relatively greater ice-age dust fluxes were not large enough to provide substantial iron fertilization to the central equatorial Pacific. This may have been because the absolute rate of dust deposition in the LGP (although greater than the Holocene rate) was very low. The lower productivity coupled with unchanged nitrate consumption suggests that the subsurface major nutrient concentrations were lower in the central equatorial Pacific during the LGP. As these nutrients are today dominantly sourced from the Subantarctic Zone of the Southern Ocean, we propose that the central equatorial Pacific data are consistent with more nutrient consumption in the Subantarctic Zone, possibly owing to iron fertilization as a result of higher absolute dust fluxes in this region (7, 8). Thus, ice-age iron fertilization in the Subantarctic Zone would have ultimately worked to lower, not raise, equatorial Pacific productivity.

The timing and dynamics of deglaciation of the Newfoundland Ice Sheet (NIS) represents a complex and poorly resolved portion of the North American Ice Sheet Complex. Establishing the flow dynamics [...]

Understanding the causes of the Pleistocene ice ages has been a significant question in climate dynamics since they were discovered in the mid-nineteenth century. The identification of orbital frequencies in [...], The covariation of carbon dioxide (C[O.sub.2]) concentration and temperature in Antarctic ice-core records suggests a close link between C[O.sub.2] and climate during the Pleistocene ice ages. The role and relative importance of C[O.sub.2] in producing these climate changes remains unclear, however, in part because the ice-core deuterium record reflects local rather than global temperature. Here we construct a record of global surface temperature from 80 proxy records and show that temperature is correlated with and generally lags C[O.sub.2] during the last (that is, the most recent) deglaciation. Differences between the respective temperature changes of the Northern Hemisphere and Southern Hemisphere parallel variations in the strength of the Atlantic meridional overturning circulation recorded in marine sediments. These observations, together with transient global climate model simulations, support the conclusion that an antiphased hemispheric temperature response to ocean circulation changes superimposed on globally in-phase warming driven by increasing C[O.sub.2] concentrations is an explanation for much of the temperature change at the end of the most recent ice age.

Sundaland, a tropical hotspot of biodiversity comprising Borneo and Sumatra among other islands, the Malay Peninsula, and a shallow sea, has been subject to dramatic environmental processes. Thus, it presents an ideal opportunity to investigate the role of environmental mechanisms in shaping species distribution and diversity. We investigated the population structure and underlying mechanisms of an insular endemic, the Bornean orangutan (Pongo pygmaeus). Phylogenetic reconstructions based on mtDNA sequences from 211 wild orangutans covering the entire range of the species indicate an unexpectedly recent common ancestor of Bornean orangutans 176 ka (95% highest posterior density, 72-322 ka), pointing to a Pleistocene refugium. High mtDNA differentiation among populations and rare haplotype sharing is consistent with a pattern of strong female philopatry. This is corroborated by isolation by distance tests, which show a significant correlation between mtDNA divergence and distance and a strong effect of rivers as barriers for female movement. Both frequency-based and Bayesian clustering analyses using as many as 25 nuclear microsatellite loci revealed a significant separation among all populations, as well as a small degree of male-mediated gene flow. This study highlights the unique effects of environmental and biological features on the evolutionary history of Bornean orangutans, a highly endangered species particularly vulnerable to future climate and anthropogenic change as an insular endemic. Asian great ape | genetic structure | radiation | geographical barriers | sociobehavioral barriers doi/ 10.1073/pnas.1010169107

The 2007 discovery of fragmentary human remains (two molars and an anterior mandible) at Zhirendong (Zhiren Cave) in South China provides insight in the processes involved in the establishment of modern humans in eastern Eurasia. The human remains are securely dated by U-series on overlying flowstones and a rich associated faunal sample to the initial Late Pleistocene, >100 kya. As such, they are the oldest modern human fossils in East Asia and predate by >60,000 y the oldest previously known modern human remains in the region. The Zhiren 3 mandible in particular presents derived modern human anterior symphyseal morphology, with a projecting tuber symphyseos, distinct mental fossae, modest lateral tubercles, and a vertical symphysis; it is separate from any known late archaic human mandible. However, it also exhibits a lingual symphyseal morphology and corpus robustness that place it close to later Pleistocene archaic humans. The age and morphology of the Zhiren Cave human remains support a modern human emergence scenario for East Asia involving dispersal with assimilation or populational continuity with gene flow. It also places the Late Pleistocene Asian emergence of modern humans in a pre-Upper Paleolithic context and raises issues concerning the long-term Late Pleistocene coexistence of late archaic and early modern humans across Eurasia. Late Pleistocene | archaic humans | mandible | chin | teeth doi/ 10.1073/pnas.1014386107

Landscapes in tectonically active regions develop in response to a complex interplay between rapid tectonic deformation and surface processes. In order to understand the evolution of these environments and distinguish between the different factors, it is fundamental to identify and quantify geomorphic processes and rates on different time scales. The forearc of south-central Chile provides an ideal setting to elucidate the response of surface processes to climatic and tectonic forcing. However, in contrast to northern Chile, this region has attracted little attention due to difficulties in quantifying the age of geomorphic surfaces. We use luminescence and stable cosmogenic nuclides ([sup.3]He, [sup.21]Ne) on conglomeratic units in the Central Depression and fluvial valley fills in the Coastal Cordillera to constrain exposure and burial ages of these units that form major landscape elements in the southern Chilean forearc. Our data indicate that disturbances in the drainage network are controlled by local uplift, which may be caused by deformation above an active blind thrust. In the Coastal Cordillera, local short-term uplift rates reach a minimum of 0.27 mm [a.sup.-1] and are on the same order as late Quaternary minimum incision rates of 0.15 mm [a.sup.-1] to 0.43 mm [a.sup.-1]. The valley fills in the Coastal Cordillera have depositional ages of 80 ka and 255 ka, respectively. Exposure ages of the extensive alluvial surfaces in the Central Depression cluster between 135 ka and 175 ka and between 240 ka and 280 ka. Hence, the deposition of these surfaces broadly coincides with marine isotope stages (MIS) 6 and 8 and appears to be climatically driven. doi: 10.1130/B26545.1

Here we present data concerning the pattern of dental development derived from the microcomputed tomography (microCT) study of a recently discovered immature hominin mandible with a mixed dentition recovered from the TD6 level of the Gran Dolina Lower Pleistocene cave site in Sierra de Atapuerca, northern Spain. These data confirm our previous results that nearly 1 million years ago at least one European hominin species had a fully modern pattern of dental development with a clear slowdown in the development of the molar field regarding the anterior dental field. Furthermore, using available information about enamel formation times and root extension rates in chimpanzees, early hominins, and modern humans, we have estimated that the formation time of the upper and lower first molars of individual 5 (H5) from TD6, which had just erupted at the time of the death of this individual, ranges between 5.3 and 6.6 y. Therefore, the eruption time of the first permanent molars (M1) in the TD6 hominins was within the range of variation of modern human populations. Because the time of M1 eruption in primates is a robust marker of life history, we suggest, as a working hypothesis, that these hominins had a prolonged childhood in the range of the variation of modern humans. If this hypothesis is true, it implies that the appearance in Homo of this important developmental biological feature and an associated increase in brain size preceded the development of the neocortical areas leading to the cognitive capabilities that are thought to be exclusive to Homo sapiens. Atapuerca | childhood | human evolution | life-history pattern doi/ 10.1073/pnas.1006772107

Using a flow domain that we constructed from 30 m digital-elevation model data of western United States and Canada and a two-dimensional numerical model for shallow-water flow over rugged terrain, we simulated outburst floods from Pleistocene Glacial Lake Missoula. We modeled a large, but not the largest, flood, using initial lake elevation at 1250 m instead of 1285 m. Rupture of the ice dam, centered on modern Lake Pend Oreille, catastrophically floods eastern Washington and rapidly fills the broad Pasco, Yakima, and Umatilla Basins. Maximum flood stage is reached in Pasco and Yakima Basins 38 h after the dam break, whereas maximum flood stage in Umatilla Basin occurs 17 h later. Drainage of these basins through narrow Columbia gorge takes an additional 445 h. For this modeled flood, peak discharges in eastern Washington range from 10 to 20 x [10.sup.6] [m.sup.3]/s. However, constrictions in Columbia gorge limit peak discharges to doi: 10. 1130/B26454.1

African wild dogs (Lycaon pictus) occupy an ecological niche characterized by hypercarnivory and cursorial hunting. Previous interpretations drawn from a limited, mostly Eurasian fossil record suggest that the evolutionary shift to cursorial hunting preceded the emergence of hypercarnivory in the Lycaon lineage. Here we describe 1.9-1.0 ma fossils from two South African sites representing a putative ancestor of the wild dog. The holotype is a nearly complete maxilla from Coopers Cave, and another specimen tentatively assigned to the new taxon, from Gladysvale, is the most nearly complete mammalian skeleton ever described from the Sterkfontein Valley, Gauteng, South Africa. The canid represented by these fossils is larger and more robust than are any of the other fossil or extant sub-Saharan canids. Unlike other purported L. pictus ancestors, it has distinct accessory cusps on its premolars and anterior accessory cuspids on its lower premolars-a trait unique to Lycaon among living canids. However, another hallmark autapomorphy of L. pictus, the tetradactyl manus, is not found in the new species; the Gladysvale skeleton includes a large first metacarpal. Thus, the anatomy of this new early member of the Lycaon branch suggests that, contrary to previous hypotheses, dietary specialization appears to have preceded cursorial hunting in the evolution of the Lycaon lineage. We assign these specimens to the taxon Lycaon sekowei n. sp.

Neandertals differ from recent and terminal Pleistocene human populations in their patterns of dental development, endostrucrural (internal structure) organization, and relative tissue proportions. Although significant changes in craniofacial and postcranial morphology have been found between the Middle Paleolithic and earlier Upper Paleolithic modern humans of western Eurasia and the terminal Pleistocene and Holocene inhabitants of the same region, most studies of dental maturation and structural morphology have compared Neandertals only to later Holocene humans. To assess whether earlier modern humans contrasted with later modern populations and possibly approached the Neandertal pattern, we used high-resolution microtomography to analyze the remarkably complete mixed dentition of the early Upper Paleolithic (Gravettian) child from Abrigo do Lagar Velho, Portugal, and compared it to a Neandertal sample, the late Upper Paleolithic (Magdalenian) child of La Madeleine, and a worldwide extant human sample. Some aspects of the dental maturational pattern and tooth endostructural organization of Lagar Velho 1 are absent from extant populations and the Magdalenian specimen and are currently documented only among Neandertals. Therefore, a simple Neandertal versus modern human dichotomy is inadequate to accommodate the morphostructural and developmental variation represented by Middle Paleolithic and earlier Upper Paleolithic populations. These data reinforce the complex nature of Neandertal-modern human similarities and differences, and document ongoing human evolution after the global establishment of modern human morphology. dentition | development | modern humans | Neandertal | Pleistocene doi/ 10.1073/pnas.0914202107

Sediment delivery rates through an entire ice age are investigated using seismic records of glacial erosion products from the Fennoscandian Ice Sheet deposited offshore of mid-Norway in the 2.7 m.y. old Naust Formation (volume 100,000 [km.sup.3]). The mean sedimentation rate over the ice age is ~0.24 m [k.y.sup.-1], with bedrock lowering of ~520 m in the ice-sheet catchment. The mean sediment delivery is 2-3 times higher for the most recent 600 k.y. than for earlier Naust sequences. The hypothesis that glacial erosion is most rapid early in an ice age, when there was presumably much weathered bedrock and preglacial sediment available, is not accepted for our study area. More important are changing ice-sheet dimensions and dynamics, varying intensity of individual glacial cycles, and complex ice-sheet dynamics in single deglaciations. The mean rate of sediment delivery from ice sheets is an order of magnitude higher than from fluvial activity in the huge Amazon and Mississippi systems, implying that ice is a very effective agent of long-term denudation during cold periods of Earth history. doi: 10.1130/G25523.1

Fossils of the giant short-faced bear, Arctodus simus (Cope, 1879), have been recovered from over 100 localities in North America, extending from Mexico to Alaska and California to Virginia. Despite this large range, the species has never been recorded from the southeastern United States. The lesser short-faced bear, Arctodus pristinus Leidy, 1854 is well represented from this region, particularly Florida, but all known occurrences are late Pliocene--middle Pleistocene in age (about 2.5 to 0.3 Ma). Differentiating A. simus from A. pristinus can be difficult because large individuals of A. pristinus overlap in size with small individuals of A. simus, and there are few morphological differences. However, these two taxa can be clearly separated based on the relative proportions of their molars and premolars. Two Pleistocene records of A. simus representing a minimum of three individuals from the Withlacoochee River drainage of central Florida are reported here, substantially extending the distribution of this massive bear into southeastern North America. A late Pleistocene age for these occurrences is corroborated by an associated Rancholabrean fauna and rare earth elemental analyses. One of the reported individuals is quite large, supporting the hypothesis of extreme sexual dimorphism in A. simus and rejecting a hypothesis of two subspecies.

High concentrations of iridium have been reported in terrestrial sediments dated at 12.9 ka and are interpreted to support an extraterrestrial impact event as the cause of the observed extinction in the Rancholabrean fauna, changes in the Paleoindian cultures, and the onset of the Younger Dryas cooling [Firestone RB, et al. (2007) Proc Natl Acad Sci USA 104:16016-16021]. Here, we report platinum group element (PGE: Os, Ir, Ru, Rh, Pt, Pd), gold (Au) concentrations, and [sup.187]Os/[sup.188]Os ratios in time-equivalent terrestrial, lacustrine, and marine sections to seek robust evidence of an extraterrestrial contribution. First, our results do not reproduce the previously reported elevated Ir concentrations. Second, [sup.187]Os/[sup.188]Os isotopic ratios in the sediment layers investigated are similar to average crustal values, indicating the absence of a significant meteoritic Os contribution to these sediments. Third, no PGE anomalies distinct from crustal signatures are present in the marine record in either the Gulf of California (DSDP 480, Guaymas Basin) or the Cariaco Basin (ODP 1002C). Our data show no evidence of an extraterrestrial (ET)-PGE enrichment anomaly in any of the investigated depositional settings investigated across North America and in one section in Belgium. The lack of a clear ET-PGE signature in this sample suite is inconsistent with the impact of a large chondritic projectile at the Belling--Allerod/Younger Dryas transition. Os isotopes | platinum group elements | Clovis | Pleistocene extinction | meteorite doi/10.1073/pnas.0908874106

Although the North American megafaunal extinctions and the formation of novel plant communities are well-known features of the last deglaciation, the causal relationships between these phenomena are unclear. Using the dung fungus Sporormiella and other paleoecological proxies from Appleman Lake, Indiana, and several New York sites, we established that the megafaunal decline closely, preceded enhanced fire regimes and the development of plant communities that have no modern analogs. The loss of keystone megaherbivores may thus have altered ecosystem structure and function by the release of palatable hardwoods from herbivory pressure and by fuel accumulation. Megafaunal populations collapsed from 14,800 to 13,700 years ago, well before the final extinctions and during the Bolling-Allerod warm period. Human impacts remain plausible, but the decline predates Younger Dryas cooling and the extraterrestrial impact event proposed to have occurred 12,900 years ago. 10.1126/science.1179504

Adaptation to different resources has the potential to cause rapid species diversification, but few studies have been able to quantify the time scale of recent adaptive radiations. The pea aphid, Acyrthosiphon pisum, a model of speciation for host-specialized parasites, consists of several biotypes (races or species) living on distinct legume hosts. To document this radiation, we used rapidly evolving sequences from Buchnera, the maternally transmitted bacterial endosymbiont of aphids. Analyses of Buchnera pseudogene sequences revealed that 11 host-associated biotypes sort mostly into distinct matrilines despite low sequence divergence. A calibration based on divergence times of 7 sequenced genomes of Buchnera allowed us to date the last maternal ancestor of these biotypes between 8,000 and 16,000 years, with a burst of diversification at an estimated 3,600-9,500 years. The recency of this diversification, which is supported by microsatellite data, implies that the pea aphid complex ranks among the most rapid adaptive radiations yet documented. This diversification coincides with post-Pleistocene warming and with the domestication and anthropogenic range expansion of several of the legume hosts of pea aphids. Thus, we hypothesize that the new availability or abundance of resources triggered a cascade of divergence events in this newly formed complex. adaptive radiation | Buchnera | ecological speciation | host races | Neolithic agriculture

Variations in the intensity of high-latitude Northern Hemisphere summer insolation, driven largely by precession of the equinoxes, are widely thought to control the timing of Late Pleistocene glacial terminations. However, recently it has been suggested that changes in Earth's obliquity may be a more important mechanism. We present a new speleothem-based North Atlantic marine chronology that shows that the penultimate glacial termination (Termination II) commenced 141,000 [+ or -] 2500 years before the present, too early to be explained by Northern Hemisphere summer insolation but consistent with changes in Earth's obliquity. Our record reveals that Terminations I and II ate separated by three obliquity cycles and that they started at near-identical obliquity phases.

The submerged Pleistocene beach conglomerate is an underwater shelly and cobble-rich formation that has been found only on the southern flanks of the English Channel. It resulted from the cementation of beach deposits that were overlain by loessic silts at a time of lower sea level. Study of the fauna within this conglomerate allows the separation of three shelly belts located between -24 and -54 m around the Channel Islands of the Normano-Breton Gulf, -40 and -65 m off Yregor, and -52 and -80 m off Leon. These belts are correlated with three regressive Pleistocene episodes. A comparison with one of Shackleton's published sea-level curves has produced age estimates that date the three beach deposits at around 105-110, 73-80 and 30-57 ka, respectively. These beaches were sealed by three phases of loess deposition around 103, 67 and 18 ka. We assume that there are at least three different Pleistocene beach conglomerates in the English Channel. Some of them show differences in their fossil fauna that could be partly a factor of contemporaneous water temperature. A fourth beach conglomerate without fossil fauna may exist at -93 m.

[1] In Sicily, the progressive imbrication of the Apenninic thrust belt above the Pelagian-African Foreland is traced by the southward migration of marine basins that were progressively shortened during the late Miocene-Pleistocene. The outermost and youngest thrust sheet (Gela Nappe) displays a peculiar shortening, with Messinian to early Pliocene E-W folds refolded in the late Pliocene early Pleistocene by approximately N-S folds (subparallel to the transport direction of the thrust sheets). This structural interference is documented in south Sicily within localized belts of refolding spaced ~5-8 km apart. The significance of this fold interference pattern is highlighted by our analysis of the offshore seismic reflection line M23A (CROP Mare Project) that intersects the Gela Nappe along a trace suborthogonal to the thrust transport direction. Migration and depth conversion of the line reveal multiple imbrications and draping of the allochthonous units above structural highs of the foreland, delimited by inherited N-S faults. The largest faults bound mid-late Miocene extensional basins but were reactivated in compression during the late Pliocene early Pleistocene, causing (1) superposed folding along discordant N-S structural trends, (2) compressional extrusion of the whole wedge of the Gela Nappe, and (3) offset of its sole thrust. The reactivation of faults subparallel to the transport direction accommodates differential flexure of the rigid foreland beneath the Apenninic wedge, and these late stage deformations in the foreland are responsible for the superposition of E-W finite shortening onto N-S shortening. Citation: Ghisetti, F. C., A. R. Gorman, M. Grasso, and L. Vezzani (2009), Imprint of foreland structure on the deformation of a thrust sheet: The Plio-Pleistocene Gela Nappe (southern Sicily, Italy), Tectonics, 28, TC4015, doi:10.1029/ 2008TC002385.

Abstract.--Published accounts of the Carpinteria avifauna, collected from an upper Pleistocene asphalt deposit near Carpinteria, California, were based on only a small portion of the collection. The present paper is [...]

The dominant period of Pleistocene glacial cycles changed during the mid-Pleistocene from 40,000 years to 100,000 years, for as yet unknown reasons. Here we present a 2.1-million-year record of sea surface partial pressure of C[O.sub.2] (PC[O.sub.2]), based on boron isotopes in planktic foraminifer shells, which suggests that the atmospheric partial pressure of C[O.sub.2] (pC[O.sub.2]) was relatively stable before the mid-Pleistocene climate transition. Glacial PC[O.sub.2] was ~31 microatmospheres higher before the transition (more than 1 million years ago), but interglacial PC[O.sub.2] was similar to that of [ate Pleistocene interglacial cycles (

The desert pocket mouse (Chaetodipus penicillatus) comprises 6 nominate subspecies that occupy warm, sandy desert-scrub habitats across the Mojave and Sonoran deserts. The most thorough morphological assessment within the species noted variable levels of distinctiveness, leading to uncertainty regarding the geographic distributions of subspecies, Subsequent genetic assessments using chromosomal, allozymic, and mitochondrial DNA (mtDNA) sequence data detected a general east-west divergence centered on the Colorado River, but few locations were included in these assessments. We investigated phylogeographic structure in C. penicillatus by sequencing regions of mtDNA for 220 individuals from 51 locations representing all continental subspecies. We identify 2 major monophyletic mtDNA lineages (clades) roughly centered in the Mojave and Sonoran deserts. These clades broadly overlap along the Lower Colorado River valley and adjacent desert regions across most of the range of C. p. penicillatus. Outside this zone of mtDNA clade overlap, Sonoran clade haplotypes occur in populations from across the range of C. p. pricei and extend to the northwestern edge of the Sonoran Desert within the southern range of C. p. angustirostris. Northern clade haplotypes occur in populations within the ranges of C. p. sobrinus and C. p. stephensi and in populations from the western Mojave Desert in the northern range of C. p. angustirostris. Based on rough estimates for rates of sequence evolution, divergence among the major clades appears to have occurred during the Pleistocene, but well before the latest glacial maximum. The secondary contact among the major clades appears to have some longevity, with little evidence of recent, postglacial range expansion. We develop ecological niche models (EMNs) for the major lineages of C. penicillatus, and project these models onto reconstructions of climatic conditions during the latest glacial maximum (LGM; 18,000-21,000 years ago). The ENMs for each clade indicate differences in predicted current geographic distributions as well as distributions during the LGM. Models for the LGM indicate broad retention of potential habitat within the area of contact among the major clades. Furthermore, the ENM for the Mojave clade in particular indicates retention of suitable habitat during the LGM in small isolated patches within northern areas, consistent with the haplotype network that supports the perspective that some populations from the Mojave clade were isolated within northern refugia during the last glacial period. Key words: Chaetodipus penicillatus, desert pocket mouse, ecological niche modeling, mitochondrial DNA, Mojave Desert, phylogeography, Sonoran Desert, subspecies

Fixed nitrogen (N) is a limiting nutrient for algae in the low-latitude ocean, and its oceanic inventory may have been higher during ice ages, thus helping to lower atmospheric C[O.sub.2] during those intervals. In organic matter within planktonic foraminifera shells in Caribbean Sea sediments, we found that the [sup.15]N/[sup.14]N ratio from the last ice age is higher than that from the current interglacial, indicating a higher nitrate [sup.15]N[sup.14]N ratio in the Caribbean thermocline. This change and other species-specific differences are best explained by less N fixation in the Atlantic during the last ice age. The fixation decrease was most likely a response to a known ice age reduction in ocean N loss, and it would have worked to balance the ocean N budget and to curb ice age--interglacial change in the N inventory.

Since its discovery in southeastern Uzbekistan in 1938, the Teshik-Tash child has been considered a Neandertal. Its affinity is important to studies of Late Pleistocene hominin growth and development as well as interpretations of the Central Asian Middle Paleolithic and the geographic distribution of Neandertals. A close examination of the original Russian monograph reveals the incompleteness of key morphologies associated with the cranial base and face and problems with the reconstruction of the Teshik-Tash cranium, making its Neandertal attribution less certain than previously assumed. This study reassesses the Neandertal status of Teshik-Tash 1 by comparing it to a sample of Neandertal, Middle and Upper Paleolithic modern humans, and recent human sub-adults. Separate examinations of the cranium and mandible are conducted using multinomial logistic regression and discriminant function analysis to assess group membership. Results of the cranial analysis group Teshik-Tash with Upper Paleolithic modern humans when variables are not size-standardized, while results of the mandibular analysis place the specimen with recent modern humans for both raw and size-standardized data. Although these results are influenced by limitations related to the incomplete nature of the comparative sample, they suggest that the morphology of Teshik-Tash 1 as expressed in craniometrics is equivocal. Although, further quantitative studies as well as additional sub-adult fossil finds from this region are needed to ascertain the morphological pattern of this specimen specifically, and Central Asian Middle Paleolithic hominins in general, these results challenge current characterizations of this territory as the eastern boundary of the Neandertal range during the Late Pleistocene. Am J Phys Anthropol 138:45-61, 2009. KEY WORDS Late Pleistocene; dispersals; sub-adult hominin fossil; logistic regression

The factors driving glacial changes in ocean overturning circulation are not well understood. On the basis of a comparison of 20 climate variables over the past four glacial cycles, the [...]

Over 60 faunal species disappeared from the Australian continent during the Middle-Late Pleistocene. Most of these animals were large to gigantic marsupials, birds and reptiles. A terminal extinction date of 46.4 kyr has been proposed for the megafauna, with all sites containing younger fossil megafauna dismissed by some researchers because of questions over stratigraphic integrity or chronologies. The timing of the extinctions is argued to be broadly coincident with estimates of first colonization of the continent by modern humans, and explanatory extinction models involving humans have subsequently gained currency. However there is considerable evidence to suggest that in some parts of the continent, people and some species of megafauna may have co-existed well beyond 46.4 kyr. In other places, such as Tasmania and the north of the continent, there is no known record of a human-megafauna temporal overlap. A review of the available evidence indicates that only 13 species of megafauna were extant on human arrival in Australia. The archaeology of this period indicates that rather than a focus on big game hunting or 'firestick farming', it was characterized by regional variability in subsistence strategies consistent with the range of environmental zones. At the present time there is no substantive argument for a terminal extinction date of 46.4 kyr, the current evidence indicating that there is no specific time period that correlates to any single mass extinction event. On the basis of available evidence arguments for either human or climatic causation are entirely circumstantial and implicitly require acceptance of many unproven assumptions. Claims to have eliminated climate as a primary driver are premature and the recent focus on delivering 'proof of human causation in Pleistocene faunal extinctions diverts attention from achieving a better understanding of the differential impacts of climate change and short term climatic flux in a land of environmental extremes. Keywords: Sahul Australia megafauna extinctions archaeology climate change

In 1907, remnants of a mammoth and a woolly rhinoceros were discovered in the Pleistocene clays of an earth-wax mine in Starunia village. Then, in 1929, a nearly fully preserved woolly rhinoceros was found in the same mine. The unique combination of clays, oil, and brine into which the animals had sunk is responsible for their almost perfect preservation. During the late Pleistocene winters, when the ice and snow cover was present in the tundra 'paleoswamp,' areas of inflow of brines, oils, and hydrocarbon gases had a higher temperature, which resulted in melting and cracking of the cover, and large mammals could be trapped. Geoelectric measurements, as well as molecular and stable isotope analyses of gases in the near-surface zone within the 'paleoswamp' performed in 2004-2005, reveal a few places favorable to the burial and preservation of Pleistocene vertebrates. Keywords: woolly rhinoceros, ozokerite, Pleistocene, surface geochemical survey, DC resistivity, stable carbon isotopes, Ukraine.

Chinese loess is regarded as one of the most detailed and complete terrestrial archives of late Cenozoic climate change. However, high-resolution optically stimulated luminescence (OSL) dates presented here reveal that the suborbital chronological framework of Chinese loess used in many previous climate reconstructions requires reassessment. Chronological uncertainty of as much as 10-15 k.y. for the late Pleistocene is largely a result of the widespread use of nonradiometric dating techniques that fail to account for site-specific depositional conditions associated with loess emplacement and diagenesis. OSL-based age models that account for these processes are used to examine detailed records of past sedimentation, as well as grain size and magnetic susceptibility proxies for late Pleistocene East Asian monsoon variation. Abrupt shifts in monsoon proxies occur over [10.sup.2]-[10.sup.3] yr time scales, potentially forced by a variety of factors and influenced by site location and site-specific changes in sedimentation. Keywords: monsoon, luminescence, radiometric dating, Loess Plateau, China, Pleistocene.

Rock varnish from late to latest Pleistocene geomorphic features in the drylands of the western U.S. provides evidence of nine millennial-scale wet events from 11,500-18,000 calendar yr B.P., represented by regionally replicable and approximately evenly spaced manganese and barium-rich dark bands in varnish microstratigraphy. Preliminary radiometric age calibration indicates that these events appear to be broadly coeval with millennial-scale cooling events identified in the Greenland Ice Sheet Project 2 (GISP2) ice core record. Six of these wet events are associated with the cold intervals of the Younger Dryas and Heinrich event H1, and the other three with the short-lived cooling phases of the Intra-Allerod Cold Period, the Older Dryas, and the Oldest Dryas. These results, combined with our previous documentation of millennial-scale wet events in the Holocene varnish record for the same region, indicate that such wet oscillations in the western U.S. may be parts of regionally widespread manifestation of well-documented, pervasive millennial-scale cycles of the North Atlantic climate. Keywords: rock varnish, wet events, cooling events, Younger Dryas, Heinrich events, western U.S.

The earlier Middle Pleistocene human partial cranium from Hulu Cave, Tangshan, Nanjing (Hulu 1) exhibits an ectocranial lesion which covers most of the anterior neurocranium, largely between the temporal lines and extending from the supratoral sulcus to the anterior parietal bone. The endocranial surfaces and the remainder of the cranium (upper facial skeleton, lateral frontal bone, posterior parietal bones, and mid-occipital bone) are norreal. The healed lesion exhibits both resorption and the lay ing down of new bone. Differential diagnosis suggests that the lesion was caused by either trauma (broad compressive trauma, tensile trauma to the scalp, or partial scalp removal) or burning (with damage to scalp and superficial neurocranium). Dietary deficiencies, infection, and neoplastic disorders do not fit the lesion characteristics. The Hulu 1 specimen therefore joins a growing sample of Pleistocene Homo remains with nonfatal and nontrivial disorders. KEY WORDS Homo erectus; frontal bone; scalp; trauma; burning

Paleontological analysis of remains from Wezmeh Cave in western Iran have yielded a Holocene Chalcolithic archeological assemblage, a rich Late Pleistocene carnivore faunal assemblage, and an isolated unerupted human maxillary premolar ([P.sup.3] or possibly [P.sup.4]). Species representation and U-series dating of faunal teeth place the carnivore assemblage during oxygen isotope stages (OIS) 3 and 2, and noninvasive gamma spectrometry dating of the human premolar places it at least as old as early OIS 2. The human premolar crown morphology is not diagnostic of late archaic versus early modern human affinities, but its buccolingual diameter places it at the upper limits of Late Pleistocene human [P.sup.3] and [P.sup.4] dimensions and separate from a terminal Pleistocene regional sample. Wezmeh Cave therefore provides additional Paleolithic human remains from the Zagros Mountains and further documents Late Pleistocene human association with otherwise carnivore-dominated cave assemblages. KEY WORDS human paleontology; modern humans; Neandertals; dentition; carnivores; Zagros

Methane (C[H.sub.4]) is an important greenhouse gas and amplifier of climate change. However, the causes of atmospheric C[H.sub.4] variations over glacial-interglacial cycles remain unresolved. We propose that microbial methanogenesis along the shallow margins of sedimentary basins provides a source of atmospheric C[H.sub.4] temporally connected with both advance and retreat of continental ice sheets. Extensive biodegradation of hydrocarbons in the Antrim Shale Formation, Michigan, United States, is associated with an active subsurface consortium of fermentative and methanogenic microorganisms. This activity was initially stimulated when saline formation waters were diluted by meltwater derived from overriding Pleistocene ice sheets. During glaciation, C[H.sub.4] produced by this community accumulated in the shale at a rate of 1 Tg C[H.sub.4] per 1000 yr as a result of ice coverage and increased hydrostatic pressure. We estimate that at present the Antrim Shale contains only 12%-25% of the cumulative mass of C[H.sub.4] generated in the shale over the Pleistocene, indicating that C[H.sub.4] that had accumulated during glaciation was subsequently released following ice-sheet retreat. While release from the Antrim Shale represents only a small part of the global C[H.sub.4] budget, when extended to other glaciated sedimentary basins, subsurface methanogenesis may generate a substantial, previously unrecognized source of atmospheric C[H.sub.4] during deglaciation. Keywords: methane, biogeochemistry, black shale, glaciation.

Previous bone collagen carbon and nitrogen isotopic studies of Late Pleistocene European cave bears (Ursus spelaeus) have shown that these bears frequently had low nitrogen isotope values, similar to those of herbivores and indicating either unusual physiology related to hibernation or a herbivorous diet. Isotopic analysis of animal bone from the Pestera cu Oase (Cave with Bones), Romania, shows that most of its cave bears had higher nitrogen isotope values than the associated herbivores and were, therefore, omnivorous. The Oase bears are securely identified as cave bears by both their morphology and DNA sequences. Although many cave bear populations may have behaved like herbivores, the Oase isotopic data demonstrate that cave bears were capable of altering their diets to become omnivores or even carnivores. These data therefore broaden the dietary profile of U. spelaeus and raise questions about the nature of the carnivore guild in Pleistocene Europe. carbon isotopes | nitrogen isotopes | diets | ancient DNA

The recent history of the Soufriere Hills volcano, Montserrat, Lesser Antilles volcanic arc, is deduced using data obtained from a submarine core collected in 2002. The core contains concentrations of ash and several tephra layers, which are identified by the abundance of glass shards, dense and poorly vesiculated particles, and scoria. The tephra layers have been dated using micropalaeontology and stable isotope stratigraphy. Tephra layers in a marine sediment core off the coast of Montserrat record the volcanic history of South Soufriere Hills-Soufriere Hills volcano back to 250 ka. Eight layers are composed of dense juvenile ash related to dome eruptions, five of which can be directly correlated to dated domes or related pyroclastic flow sequences on land. Six layers are composed of pumiceous glassy ash and relate to significant explosive eruptions. A marker sequence of basalt tephra layers is dated at 124-147 ka and is correlated with construction of the South Soufriere Hills basaltic stratocone. Pelagic sediments between the main tephra layers have low abundances of volcanogenic components (

The role of Pleistocene forest refugia and rivers in the evolutionary diversification of tropical biota has been the subject of considerable debate. A range-wide analysis of gorilla mitochondrial and nuclear variation was used to test the potential role of both refugia and rivers in shaping genetic diversity in current populations. Results reveal strong patterns of regional differentiation that are consistent with refugial hypotheses for central Africa. Four major mitochondrial haplogroups are evident with the greatest divergence between eastern (A, B) and western (C, D) gorillas. Coalescent simulations reject a model of recent east-west separation during the last glacial maximum but are consistent with a divergence time within the Pleistocene. Microsatellite data also support a similar regional pattern of population genetic structure. Signatures of demographic expansion were detected in eastern lowland (B) and Gabon/Congo (D3) mitochondrial haplogroups and are consistent with a history of postglacial expansion from formerly isolated refugia. Although most mitochondrial haplogroups are regionally defined, limited admixture is evident between neighboring haplogroups. Mantel tests reveal a significant isolation-by-distance effect among western lowland gorilla populations. However, mitochondrial genetic distances also correlate with the distance required to circumnavigate intervening rivers, indicating a possible role for rivers in partitioning gorilla genetic diversity. Comparative data are needed to evaluate the importance of both mechanisms of vicariance in other African rainforest taxa. control region | mitochondrial | phylogeography | refugium

Extremely arid conditions in tropical Africa occurred in several discrete episodes between 135 and 90 ka, as demonstrated by lake core and seismic records from multiple basins [Scholz CA, Johnson TC, Cohen AS, King JW, Peck J, Overpeck Jr, Talbot MR, Brown ET, Kalindekafe L, Amoako PYO, et al. (2007) Proc Natl Acad Sci USA 104:16416-16421]. This resulted in extraordinarily low lake levels, even in Africa's deepest lakes. On the basis of well dated paleoecological records from Lake Malawi, which reflect both local and regional conditions, we show that this aridity had severe consequences for terrestrial and aquatic ecosystems. During the most arid phase, there was extremely low pollen production and limited charred-particle deposition, indicating insufficient vegetation to maintain substantial fires, and the Lake Malawi watershed experienced cool, semidesert conditions ( cichlid evolution | Lake Malawi | Out-of-Africa Hypothesis | paleoclimate | paleolimnology

The environmental backdrop to the evolution and spread of early Homo sapiens in East Africa is known mainly from isolated outcrops and distant marine sediment cores. Here we present results from new scientific drill cores from Lake Malawi, the first long and continuous, high-fidelity records of tropical climate change from the continent itself. Our record shows periods of severe aridity between 135 and 75 thousand years (kyr) ago, when the lake's water volume was reduced by at least 95%. Surprisingly, these intervals of pronounced tropical African aridity in the early late-Pleistocene were much more severe than the Last Glacial Maximum (LGM), the period previously recognized as one of the most arid of the Quaternary. From these cores and from records from Lakes Tanganyika (East Africa) and Bosumtwi (West Africa), we document a major rise in water levels and a shift to more humid conditions over much of tropical Africa after [approximately equal to] 70 kyr ago. This transition to wetter, more stable conditions coincides with diminished orbital eccentricity, and a reduction in precession-dominated climatic extremes. The observed climate mode switch to decreased environmental variability is consistent with terrestrial and marine records from in and around tropical Africa, but our records provide evidence for dramatically wetter conditions after 70 kyr ago. Such climate change may have stimulated the expansion and migrations of early modern human populations. human origins | Lake Malawi | paleoclimate | Pleistocene

A carbon-rich black layer, dating to [approximately equal to] 12.9 ka, has been previously identified at [approximately equal to] 50 Clovis-age sites across North America and appears contemporaneous with the abrupt onset of Younger Dryas (YD) cooling. The in situ bones of extinct Pleistocene megafauna, along with Clovis tool assemblages, occur below this black layer but not within or above it. Causes for the extinctions, YD cooling, and termination of Clovis culture have long been controversial. In this paper, we provide evidence for an extraterrestrial (ET) impact event at [congruent to] 12.9 ka, which we hypothesize caused abrupt environmental changes that contributed to YD cooling, major ecological reorganization, broad-scale extinctions, and rapid human behavioral shifts at the end of the Clovis Period. Clovis-age sites in North American are overlain by a thin, discrete layer with varying peak abundances of (i) magnetic grains with iridium, (ii) magnetic microspherules, (iii) charcoal, (iv) soot, (v) carbon spherules, (vi) glass-like carbon containing nanodiamonds, and (vii) fullerenes with ET helium, all of which are evidence for an ET impact and associated biomass burning at [approximately equal to] 12.9 ka. This layer also extends throughout at least 15 Carolina Bays, which are unique, elliptical depressions, oriented to the northwest across the Atlantic Coastal Plain. We propose that one or more large, low-density ET objects exploded over northern North America, partially destabilizing the Laurentide Ice Sheet and triggering YD cooling. The shock wave, thermal pulse, and event-related environmental effects (e.g., extensive biomass burning and food limitations) contributed to end-Pleistocene megafaunal extinctions and adaptive shifts among PaleoAmericans in North America. comet | iridium | micrometeorites | nanodiamonds | spherules